3 ms·

Good point. The class definitions can easily be changed from float to double in just a few lines. I used to use a lot of doubles. The I wrote some DirectX and

Good point. The class definitions can easily be changed from float to double in just a few lines. I used to use a lot of doubles. The I wrote some DirectX and GPUs all use float. I figured if floats are good enough for 3D, they're good enough for me :o)

jcranmer 7y ago
With floating-point code, you will slowly lose precision in your numbers. (How quickly is a matter of what calculations you're doing, if you're doing them in an error-tolerant manner, and how bad the initial error is in the first place). Single-precision floating-point starts you off with about 6-7 decimal digits of precision, and the intermediate rounding will mean that you're constantly introducing error in the 7th digit. Computer graphics are pretty tolerant of error--you only need about a 1-2 digits of precision generally--and achieving higher FLOPS is more useful than higher precision. Engineering tolerances are usually going to be tighter, perhaps 4-5 digits for particularly tight tolerances. Furthermore, you're more likely to use nastier equations (logarithms and exponents are particularly bad for precision), so single-precision could well introduce error with real-world consequences.
- vardump 7y ago
  Yup. Although I'd like to add a typical issue when there's a small change in a large quantity. Say time. If you measure time in microseconds, and use floats, your precision will be halved to 2 us in just 33.5 seconds. In 24 hours, the precision has detoriated to over 2 milliseconds. One famous example is the deadly Patriot missile bug: https://sdqweb.ipd.kit.edu/publications/pdfs/saglam2016a.pdf https://sdqweb.ipd.kit.edu/publications/pdfs/saglam2016a.pdf > Furthermore, you're more likely to use nastier equations (logarithms and exponents are particularly bad for precision), so single-precision could well introduce error with real-world consequences. Some other ones are iteration and simply long computation chains introducing systematic error.

jcranmer 7y ago

With floating-point code, you will slowly lose precision in your numbers. (How quickly is a matter of what calculations you're doing, if you're doing them in an error-tolerant manner, and how bad the initial error is in the first place). Single-precision floating-point starts you off with about 6-7 decimal digits of precision, and the intermediate rounding will mean that you're constantly introducing error in the 7th digit. Computer graphics are pretty tolerant of error--you only need about a 1-2 digits of precision generally--and achieving higher FLOPS is more useful than higher precision. Engineering tolerances are usually going to be tighter, perhaps 4-5 digits for particularly tight tolerances. Furthermore, you're more likely to use nastier equations (logarithms and exponents are particularly bad for precision), so single-precision could well introduce error with real-world consequences.

vardump 7y ago
Yup. Although I'd like to add a typical issue when there's a small change in a large quantity. Say time. If you measure time in microseconds, and use floats, your precision will be halved to 2 us in just 33.5 seconds. In 24 hours, the precision has detoriated to over 2 milliseconds. One famous example is the deadly Patriot missile bug: https://sdqweb.ipd.kit.edu/publications/pdfs/saglam2016a.pdf https://sdqweb.ipd.kit.edu/publications/pdfs/saglam2016a.pdf > Furthermore, you're more likely to use nastier equations (logarithms and exponents are particularly bad for precision), so single-precision could well introduce error with real-world consequences. Some other ones are iteration and simply long computation chains introducing systematic error.